The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2001-283784 filed on Sep. 18, 2001 the entire contents thereof is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a jet propulsion boat having a jet propulsion apparatus at the stern, a jet nozzle for jetting water, which is provided in the rear portion of the jet propulsion apparatus, and a steering nozzle swingably supported by the jet nozzle to adjust the direction of a stream of water jetted from the jet nozzle.
2. Description of Background Art
A jet propulsion boat is disclosed in Japanese Unexamined Patent Application No. Hei-2-254094, entitled xe2x80x9cForward/Rearward Travel Switching Apparatus of Water Jet Boat Propulsion Apparatus.xe2x80x9d FIG. 10 is a copy of FIG. 1 of this publication with the reference numerals added to designate the parts thereof. This type of jet propulsion boat will be described in detail with reference to FIG. 10.
FIG. 10 is a cross section of a conventional jet propulsion boat. A jet propulsion boat 100 has a jet propulsion apparatus 102 at the stern 101. A jet nozzle 103 is provided at the rear portion of the jet propulsion apparatus 102 with an outlet 103a side of the jet nozzle 103 being covered with an inlet 104a side of a steering nozzle 104. The inlet 104a side of the steering nozzle 104 and the outlet 103a side of the jet nozzle 103 are swingably coupled to each other by upper and lower supporting bolts 105 and 105.
The jet propulsion boat 100 can be propelled by driving an impeller 102a of the jet propulsion apparatus 102 to thereby take water from an intake port 106, jetting the water from the jet nozzle 103, and jetting the jetted water from an outlet 104b of the steering nozzle 104.
At the time of propulsion of the jet propulsion boat 100, by swinging the steering nozzle 104 from side to side by using the upper and lower supporting bolts 105 and 105 as a center, the jet propulsion boat 100 can be turned from side to side.
In the jet propulsion boat 100, when the steering nozzle 104 is swung from side to side by using the upper and lower supporting bolts 105 and 105 as a center, it is necessary to prevent that the inner circumference on the inlet 104a side of the steering nozzle 104 interferes with the outer circumference on the outlet 103a side of the jet nozzle 103.
Consequently, the inner circumference on the inlet 104a side of the steering nozzle 104 has to be set apart from the outer circumference on the outlet 103a side of the jet nozzle 103 by some distance.
The outer circumference on the inlet 104a side of the steering nozzle 104 therefore becomes relatively large, and it disturbs the steering nozzle 104 that is disposed close to the boat bottom 101.
When the steering nozzle 104 is positioned apart from the boat bottom 101, the impeller 102a of the jet propulsion apparatus 102 is provided in a high position. Consequently, the curvature of the intake path from the intake port 106 to the impeller 102a increases, so that it becomes difficult to smoothly introduce the taken water to the impeller 102a side. For example, a cavitation occurs in the jet propulsion apparatus 102 and it hinders the jet propulsion boat 100 from being efficiently propelled.
An object of the invention is therefore to provide a jet propulsion boat which can be efficiently propelled by disposing a steering nozzle closer to the bottom of the boat.
To achieve the object, the present invention provides a jet propulsion boat including a jet propulsion apparatus driven by an engine at the stern, a jet nozzle for jetting water, which is provided in the rear portion of the jet propulsion apparatus, and a steering nozzle swingably supported by the jet nozzle so as to adjust the direction of a stream of water jetted from the jet nozzle, and the jet propulsion boat includes an outlet of the jet nozzle that is covered with an inlet of the steering nozzle, and the vertical diameter of the inlet of the steering nozzle is set to be smaller than the transverse diameter of the inlet.
By setting the vertical diameter of the inlet of the steering nozzle to be smaller than the transverse diameter, the steering nozzle can be disposed closer to the boat bottom. The jet propulsion apparatus can be accordingly disposed closer to the boat bottom with the curvature of the intake path extending from the intake port to the jet propulsion apparatus that can be flattened and with the intake path being formed in a gentle curve.
Consequently, water taken from the intake port can be smoothly directed to the jet propulsion apparatus, so that, for example, the occurrence of a cavitation can be prevented and water can be jetted efficiently.
In addition, by setting the vertical diameter to be smaller than the transverse diameter, the transverse diameter can be assured to be large. Consequently, the steering angle of the steering nozzle can be assured to a specified amount and the steering performance of the jet propulsion boat can be assured sufficiently.
To favorably propel the jet propulsion boat, the nozzle for jetting water has preferably a circular shape. In the present invention, therefore, the outlet of the jet nozzle is covered with the inlet of the steering nozzle.
With the configuration, even when the vertical diameter of the inlet of the steering nozzle is smaller than the transverse diameter, this portion can be disconnected from the water stream. Therefore, exertion of an adverse influence onto the stream of water in the nozzle can be prevented.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.